"This is a two-stage missile carrying two engines with combined solid fuel," Najjar said.
He said that Iran is ready to defend itself against any attacker.
"This missile test is in the framework of Iran's deterrent doctrine," the official IRNA news agency quoted Najjar as saying.
"It will only land on the heads of those enemies ... who want to make an aggression and invade the Islamic Republic."
Barack Obama, the US president-elect, like George Bush, the outgoing US president, has not ruled out military action although Obama has criticised the Bush administration for not pursuing more diplomacy and engagement with Tehran.
The US accuses Iran of seeking to build atomic bombs, while Iran says it only aims to generate electricity.
Iran has said it would respond to any attack by targeting US interests and Israel, as well as by closing the Strait of Hormuz, a vital route for world oil supplies.